burroughs B 9489 User manual

B9489
FLEXIBLE DISK DRIVE
TECHNICAL
MANUAL
Burroughs m
FIELD ENGINEERING
FIELD ENGINEERING PROPRIETARY DATA.
The information contained in this document is proprietary to Burroughs Corporation. The information
or this document is not to be reproduced. shown, or disclosed outside Burroughs Corporation without
written permission
of the Patent Division.
This material
is furnished for Burroughs Field Engineering Personnel. and is not furnished to customers
except
under special License Agreement.. .
THIS DOCUMENT IS THE PROPERTY OF AND SHALL BE RETURNED TO BURROUGHS
CORPORATION. BURROUGHS PLACE, DETROIT~ MICHIGAN 48232.
F.E. Dist. Code~
Printed In U.s. America December
1979 (\
1
2
3
INTRODUCTION
AND
OPERATION
FUNCTIONAL
DETAIL
.CIRCUIT
4 ADJUSTMENTS
5
6
7
8
9
10
A
B
c
MAINTENANCE
PROCEDURES
INSTALLATION
PROCEDURES
For Library Binder 424
Form 2102141-001

ii
Burroughs believes that the information described in this
manual
is accurate and reliable, and much care has been
taken inits preparation. However, no responsibility, financial
or otherwise,
is accepted for any consequences arising out of
the use of this material. The information contained herein is
subject to change. Revisions may be issued to advise of such
changes and/or additions.
Correspondence regarding this document should be addressed directly
to TechnicalDocumentationDepartment, Technical Information Organ-
ization, Burroughs Machines limited, Cumbernauld, Glasgow, Scotland,
G680LN.

Bu.rronghs
PUBLICATION
CHANGE
NOTICE
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Date: __
J
_an_ua_ry_l_9_80 _____ _
Publication Title: B 9489 Flexible Disk Drive Technical Manual
Other Affected Publications:~N_on_e _____ ~~_~ ________________ ~
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Remove the following pages :
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FIELD ENGINEERING PROPRIETARY DATA
The information contained in this document is proprietary to Burroughs Corporation. The information or
this document is not to be reproduced, shown, or disclosed outside Burroughs Corporation without written
permission of the Patent Division.
This material
is furnished for Burroughs Field Engineering Personnel, and is not furnished to customers
except under special License Agreement.
THIS DOCUMENT IS THE PROPERTY OF AND SHALL BE RETURNED TO
BURROUGHS CORPORATION, BURROUGHS PLACE, DETROIT, MICHIGAN 48232.
F.E. DiSI., SO
Code 1.... _____ _
Printed in U.S. America
iii
For Library Binder424
Form 2102141

Bu.rrou.ghs
2102141-001peN No.: __________________ _
PUBLICATION
CHANGE
NOTICE
Date: __ De_c_e_m_b_er_19_7......;9 _____ _
Publication Title: _..4:B!:...I9~4.:.:;8~9....!iFll..t.e:...!X1.!:t.·b~1~e...t:::D~isk~Dt;::;,jnu.·vue~t~e~c!.!:ihnwi~cal~Mwan~u_alk...._ ________________ _
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Retain this PCN as a record of changes made to the basic publication.
FIELD ENGINEERING PROPRIETARY DATA
The information contained in this document is proprietary to Burroughs Corporation. The information or
this document is not to be reproduced, shown, or disclosed outside Burroughs Corporation without written
permission of the Patent Division.
This material
is furnished for Burroughs Field Engineering Personnel, and is not furnished to customer.
except under special License Agreement.
THIS DOCUMENT IS THE PROPERTY OF AND SHALL BE RETURNED TO
BURROUGHS CORPORATION, BURROUGHS PLACE, DETROIT, MICHIGAN 48232.
F.E. DiSI., BD
C()de~. _____ ..I
Printed in U.S. America
iii
For Library Binder 424
Form 2102141-001

Burroughs - B 9489 Flexible Disk Drive Teclmical Manual
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Burroughs -B9489 Flexible Disk Drive Technical Mariual
Section 1
INTRODUCTION AND OPERATION
General Description. •
Configurations.
Applications .
Major Assemblies.
Motor and Spindle
Receiver. . • . .
Stepper Motor and Leadscrew. . .
Carriage. . .
Pressure Pads . .
Magnetic Heads
Recording Mode .
Printed Circuit Board
Operation . . . . .
Flexible Disk (Mini-Disk)
Sector Configuration. .
Data Configuration
Recording Mode . . . . . .
Functions
Seek
..
Write. . .
Read
..
Physical and Electrical Characteristics •
Physical. . . . . .
Electrical . . . . .
Recording Characteristics
Format. .
Data Access.
Flexible Disk .
Jacket . . .
Disk Handling. . .
Operating Procedures . . . .
Indicators and
Control. .
Electrical Interconnections, Host
to
Master Interface. . . . . . .
Master
DC Supplies. . . . ...
Master Drive to Slave Drive Interface
Line Power and Grounding. . . . .
Section 2
.FUNCTIONAL DETAIL
Positioner . . . . . • •
General Description. . . • .
Mechanics
,; • . . . • . .
Carriage. .. ..•.
Magnetic Heads . • .
Electronics.. .•••
File OP. . .
Address Latches .
Address 00 Detector. .
Illegal Address. . . • . .
Current Address Counter and Comparator
2102141-001
TABLE OF CONTENTS
Page
1 .... 1
1-2
1-2
1-3
1-3
1-3
1-3
1-4
1-4
1-4
1-4
1-5
1-5
1-5
1-5
1-6
1-6
1-7
1-7
1-7
1-7
1-7
1-7
1-7
1-7
1-7
1-7
1-8
1-8
1-8
1-9
1-9
1-9
1-10
1-10
1-10
2-1
2-1
2-1
2-2
2-2
2-2
2~3
2-4
2':"'"4
2-4
2-4
Section 2 (Continued)
. Stepper Motor Drivers .
Stepper Motor Register.
Stepper Motor. ••.• • •
Positioner Clock. .
Clock
Control. .
Direction Control. .
Position Settled .
Head Select. . . . .
Head Load Solenoids and Tiler .
Index and Sector Pulses. .
Write. . . . .
General. . . .
Write Clock. . • . .
Write Data Encode .
Unit Selection. . .
Write Inhibit • . .
Write and Erase Drivers. .
Read Head Select. . . . . •
Read Channel. . . • • •
Digital Fi Iter. • . . • •
Data Decode .
General. . •
Selection . . .
Standardizer and PLL •
PLL
.....•
Read Enable Delay .
Read Clock.
Data Window
Section 3
CIRCUIT DETAIL
General. . .
Section 4
ADJUSTMENTS
Introduction . .
Special Tools . .
Align me nt Pisk . . • .
B80 Hex Keyboard Collated Table • •
Alignment Track Selection using B80 MTR
Alignment Meter Operating Instructions
Adjustments • . • • • . • . •
Backlash Nut Adjustment.. . • . .
Track
to Track Alignment Check
Track to Track Alignment Adjustment.
Circumferential Alignment . . . •
Track 00 Adjustment • . • • • .
Phase Locked Loop and Data Windows.
DTM
·1000 or BDM 1250
DTM 1000 . . .
BDM 1250. . . . . . . . . .
Section 5
MAINTENANCE PROCEDURES
Removal and Replacement Procedures. .
Page
2-6
2-6
2-8
2-8
2-9
2-9
2-9
2-11
2-11
2-11
2-15
2-15
2-16
2-16
2-18
2-18
2-18
2-18
2-18
2-21
2-21
2-21
2-21
2-23
2-23
2-23
2-25
2-25
3-1
4-1
4-1
4-1
4-1
4-1
4-2
4-2
4-2
4-3
4-3
4-5
4-7
4-7
4-8
4-9
4-9
5-1
v

Burroughs -B9489 Flexible Disk Drive Technical Manual
TABLE OF CONTENTS (Continued)
Section 5 (Continued)
Fascia . . .
Receiver. . . . • . .
Stepper Motor and Carriage .
Head Solenoids
I..arnps . . . . . . . . . . .
Pressure Pads . .
..'
Drive Belt . .
Page
5-1
5-1
5-1
5-2
5-2
5-2
5-2
Section 5 (Continued)
Preventive Maintenance Fuide. . . . .
Fault
Finding. . . . . .
Recovery
of Conta~inated Disks.
Certified Disks. . . . . . . . . .
Section 6
INSTALLATION PROCEDURES
Installation Procedures. . .
LIST OF ILLUSTRATIONS
Figure
Page
Figure
I-I
Complete Unit.
1-1
2-16
Read Block Diagram.
1-2
Master/Slave Configuration.
1-2
2-17 Read Channel Test Points .
1-3
Major Assemblies.
1-2
2-18
Schematic -Read Channel
1-4
Stepper Motor and Leadscrew.
1-3
2-19
PLL/Data Relationship.
1-5
Carriage Assembly
1-4
2-20 Data Decode Timing.
1-6
Diagrammatic Recording Head
1-4
2-21
Schematic -Read Data Decode .
1-7
Magnetic Head Layout .
1-5
2-22 Worst Case Peak Shift
1-8
Head Schematic
1-5
1-9
Track Format (Upper Side)
1-5
3-1 Logic Example
1-10
Track Format (Lower Side)
1-5
3-2 SN7400 QJ.lad 2-Input NAND Gate .
1-11
Sector Configuration
1-6
3-3
SN7402 Quad 2-Input NOR Gate
1-12
Encoding Comparison
1-6
3-4
SN7404 HEX Inverter
~
1-13 Disk.
1-8
3-5 SN7405 HEX Inverter with Open
1-14 Jacket
1-8
Collector Output
.'
1-15
Operator Controls
1-9
3-6
SN7410 Triple 3-Input NAND Gate.
1-16
Common Electronics
1-11
3-7 SN7420 Dual 4-Input NAND Gate .
1-17 Block Diagram. 1-12
3-8
SN7426 Quad 2-Input High Input
Voltage Interface NAND Gate with Open
2-1
Positioner Mechanics (Top View)
2-1
Collector Output
2-2 . Carriage (Side View) .
2-2
3-9
SN7438 Quad 2-Input Interface NAND
2-3
Positioner Electronics Block Diagram .
2-3
Gate with Open Collector Output .
2-4
Schematic -Address Counter/
3-10
SN74132 Quad 2-Input NAND Gate
Comparator
2-5
-Schmitt Triggers
2-5
Schematic -Positioner Clock and
3-11
SN7427 Triple 3-Input NOR Gate
Stepper Motor Drivers.
2-7
3-12
SN75452 Dual NAND Driver .
2-6
Stepper Motor. ,
2-8
3-13
SN7474 Dual D-type Flip Flop
2-7
Positioner Clock Start-Up .
2-8
3-14 ITT96015D Retriggerable Monostable
2-8
Schematic - Head Load Control.
2-12
Multivibrator.
2-9
Schematic -Index/Sector J:lulses.
2-13
3-15 9602 Dual Retriggerable, Resettable,
2-10
Index and Sector Generation.
2-14
Monostable Multivibrator.
2-11
Write Block Diagram.
2-15
3-16
8284 Hexadecimal Up/Down Counter.
2-12 Write Timing
2-16
3-17 9308 Dual 4-Bit Latch .
2-13 Schematic -Write Data Encoder.
2-17
3-18 9322 Quad 2-Input Multiplexor .
2-14
Schematic -External Interface Logic. 2-19
3-19 9324 5-Bit Comparator.
2-15
Schematic -Write Driver .
2-20
3-20 733 Differential Amplifier.
vi
page
5-2
5-2
5-2
5-2
6-1
Page
2-21
2-21
2-22
2-23
2-23
2-24
2-25
3-1
3-2
3-~
3-2
3-3
3-3
.3-3
3-3
3-4
3-4
3-4
3-4
3-5
3-5
3-5
3-6
3-6
3-6
3-6
3-7

I
Figure
3-21
3-22
3-23
3-24
3-25
3-26
3-27
4--1
4--2
Burroughs - B 9489 Flexible Disk Drive Technical Manual
LIST OF ILLUSTRATIONS (Continued)
Page Figure
710 High Speed Differential Comparator
3-7
4--3 Oscilloscope Wave Form
7496 5-Bit Shift Register
3-7
4--4 Component Layout Showing the Posi-
NE 562B Phase Locked Loop.
3-8
tion of Recommended Test Point
TIL 31 or 1A48B Photo Emissive Diode
3-9
4--5 Correct Waveform
TIL
81 or 2B50B Silicon Photo Transistor
3-9
4--6 Incorrect Waveforms
Delay Une 300ns.
3-9
4--7 Unstable Waveforms
High Power Transistor 2N6055 or 4--8 Data Window Adjustment .
TIP640.
3-9
5-1 Stepper Motor and Carriage Assembly .
Backlash Nut
Adjustment.
4--2
5-2
50/60Hz Conversion.
Locking Plate Clearance 4--3
5-3
Connection Block Diagram.
LIST OF TABLES
Page
Table
1-1 Logic Interface Between Host System
1-2
2-1
3-1
4--1
4--2
5-1
and Master Drive . . . . .
DC Supplies to the Master Drive. .
Stepper Truth
Table. .
Index
of Modules.
PCB Test Points
1-9
1-10
2-6
3-1
4--1
4-2
5-3
2102141-001
Page
4--6
4--6
4--8
4--8
4--8
4--9
5-1
5-·2
5-4
I
vii

Burroughs -B9489 Flexible Oisk Drive Technical Manual Sec. 1
Page 1
SECTION 1
INTRODUCTION AND OPERATION
GENERAL DESCRIPTION
The A/B 9489 Flexible Disk Drive provides a storage
capacity
of 1 megabyte per disk. The disks are removable,
allowing unlimited off-line storage and easy transportation
of data between sites.
The disks are made from flexible mylar and are
coated with iron oxide on
both sides. A protective en-
velope shields the disk from contamination. Data is re-
corded on both sides of the disk by two heads, one for
each side. The heads are mounted on a carriage
that is
movable, so that the heads are positioned to one of the
88 concentric tracks on the disk. Movement
of the
carriage
is controlled by a stepper motor connec.ted to a
lead screw.
Writing or reading
is accomplished with the head
that is in contact with the disk. To ensure contact, a press-
Ute pad presses· the disk against the head from the opposite
side
of the disk. In order to reduce wear, the pressure pads
are retracted
if the unit is not in use. Only one pressure
pad can be active at any time.
Each disk has 2 recording sides with 88 tracks
on
each side. Each track contains 32 sectors with 180 bytes
of information in each sector.
Figure
1-1. Complete unit
For Form 2102141

Page 2 Burroughs -B9489 Flexible Disk Drive Technical Manual
Introduction and Operation
CONFIGURATIONS
Two units of the Flexible Disk Drive are available:
Master Unit (A/B
9489-1)
Slave Unit (A/B 9489-2)
The master unit is connected to the system controller
(10 Control, Device Dependent Port) and contains addition-
al electronics common to both units. The slave unit, if re-
quired, cannot function alone and connects to the master
unit. The slave unit obtains
DC power from the master
unit.
SYSTEM
MINI DISK UNITS
1/0 CABLE
I/O
.
I SLAVE
MASTER
CONTROL I
~
~
I
I
A/B 9489-1
A/B 9489-2
I
I DC
I
I
POWER
AC
I
SUPPLY
I
I
I
Figure 1-2. Master/Slave Configuration
WRITE LOCKOUT
TRANSDUCER
STEPPER MOTOR MOTOR
APPLICATIONS
Each sector of the disk (180 bytes) has a unique
address consisting
of a side track and sector number. Any
sector can be accessed by moving the head
to the correct
track
and then waiting until the correct sector arrives under
the head. This enables any sector to be accessed indepen-
dently
and is known as RANDOM ACCESS. Random
access permits selective reading or writing
of records within
a file without having to read or write the entire file (as
is the
case with magnetic tape).
Random access makes the unit ideal for memory
expansion
of small computer systems where programs and
software need
to be read into memory at frequent intervals.
In such a system the master disk would be used to contain
system software and program and the slave would be used
to record users files such as inventory, payroll, and account-
ing information.
In this application, the systems disk
is a semi-
permanent fixture while the user selects the second disk
according
to the programs required to run. Other uses are
as follows:
Software/program transportation.
Collection of diagnostic information.
Data collection.
UPPER PRESSURE
PAD SOLENOID
MAGNETIC HEADS
AND PRESSURE PADS
INDEX/SECTOR
TRANSDUCER
Figure 1-3. Major Assemblies

Burroughs -B9489 Flexible Disk prive Technical Manual Sec. 1
Page 3
Introduction and Operation
MAJOR ASSEMBLIES (Refer to figure 1-3).
MOTOR AND SPINDLE
The ac motor (115Vac) drives the spindle at 370
rpm via a pulley and self tensioning belt. The purpose of
the spindle is to rotate the disk and it is cone shaped to
center the disk as the disk is engaged with the spindle.
Conversion from 50Hz to 60Hz is achieved by reversing
the pulley on the motor shaft.
RECEIVER
The receiver accepts and holds the disk in the unit.
It has two positions, up when the door is open, and down
when the door
is closed. When the door is open and the
receiver
is up, disks may be inserted or extracted. When
the door
is closed and the receiver down, the disk is not
accessable
to the operator and is in use by the unit.
The receiver operates as follows:
1. Accepts the disk when it is inserted.
2. Lowers the disk when the door
is closed.
3. Engages the disk with the spindle by means
of
the annulus.
4. The index/sector transducer provides timing
pulses for use
of the controller. .
5. The write inhibit transducer detects, disks
which are write protected.
6. Provides a mounting for the upper pressure
pad solenoid.
7. Swi~ches the motor ON when the receiver
lowers and OFF when the receiver lifts.
8. Lifts the upper head clear
of the disk when in
the up position
to enable easy insertion and
extraction
of the disk.
STEPPER MOTOR AND LEADSCREW
The purpose of the stepper motor and lead screw is
to move the carriage to the required track. The stepper
motor
is three phase (3 windings) with 15 degrees per step.
If the windings are energised in the correct sequence the
motor will step in one direction and if the sequence is re-
versed, the motor will step in the other direction. The lead
screw
is an integral part of the motor and is a "Three Start
Leadscrew". Each step
of the motor corresponds to a
1/64 inch movement of the carriage.
Figure
1-4. Stepper Motor and Leadscrew
For Form 2102141

Page 4 Burroughs -B9489 Flexible Disk Drive Technical Manual
Introduction and Operation
CARRIAGE
The purpose of the carriage is to hold the heads in
the correct position. The carriage
is threaded on the lead
screw so that
as the lead screw rotates, the carriage moves
towards, or away from, the spindle. An alignment rod
prevents rotation
of the carriage with the lead screw.
The backlash
nut ensures that all play between the
leadscrew
and carriage is taken up in the direction of the
spindle.
The vane interrupts the track
00 transducer when
the carriage
is situated at track 00. This is used to calibrate
the electronics when a disk
is first inserted and each time
track
00 is accessed.
The lower magnetic head
is bonded to the body of
the carriage. The upper magnetic head is bonded to an arm
which can move vertically. This arm
is lifted when the re-
ceiver
is raised to allow the disk to pass between the heads.
When the receiver
is lowered, the arm is returned to its
position by spring tension.
PRESSURE PADS
The magnetic head pressure pads are mounted on
the carriage and press the disk against the head to ensure
good contact. A force of 11 grams is provided by the
torsion springs. The pressure pads are only active when
their respective solenoids are selected. Only one solenoid
can
be picked at any time. (A function of the electronics).
When a head
is selected, the pressure pad solenoid on the
opposite side
of the disk is energised, allowing the pressure
pad
to push the disk against the selected head. 5 revolu-
Figure
1-5. Carriage Assembly
tions after the read or write operation the pressure
pad is,
disengaged
if no further commands are received. This
reduces disk
and head wear.
MAGNETIC HEADS
The magnetic heads contain 2 windings, one for
writing
and reading and'one for erase. Writing is achieved
by passing current through the write/read winding. When
current passes through the winding, a magnetic flux flows
in the core. In the area of the gap the region of least re-
luctance to the magnetic flux
is through the disk. Flux
passing through the disk magnetises it permanently, com-
pletelysaturating it. (refer
to figure 1-6). By reversing the
current in the winding, the direction
of magnetisation is
reversed. A change in direction of magnetisation is known
as a "flux reversal."
By writing flux reversals in a specific pattern, data
can be recorded.
RECORDING MODE (Refer to the paragraph)
During read, the flux reversals passing under the head
flow through the core and induce a current in the winding.
The induced current
is amplified'and decoded into the
original data. Read
is non-destructive and the data can be
read repeatedly.
The purpose
of the erase winding is to magnetise a
band on each side
of the data. This erases any flux left from
previous writing operations
and provides a "guard band".
If old data was allowed in this position a slight misposition
of the head would pick up both sets of data and result in
errors.
WINDING __ ~"
MAGNETIC
FLUX
DISK MOVEMENT
CORE
MAGNETIC
COATI1 NG
DISK
Figure 1-6. Diagrammatic Recording Head

Burroughs -B9489 Flexible Dis~ Drive Technical Manual Sec. 1
Page 5
Introduction and Operation
Refer to figure 1-7 The recorded data is approxi-
mately 0.0104 inch wide with a guard band of 0.0052
inch on each side. This type of head is known as a single
gap, tunnel erase head.
The cores are mounted in a ceramic shoe for long
life. Figure
1-8 is an electrical schematic of the magnetic
head.
PRINTED CIRCUIT BOARD
The master printed circuit board contains the
following:
1.
2.
3.
4.
5.
6.
7.
8.
Interface electronics
Positioner electronics
Index/Sector pulses
Write encoding
Write amplifier
Read amplifier
Read decoding
Write lockout
The slave printed circuit board contains the follow-
ing:
1. Positioner electronics
2. Write amplifier
3. Write lockout
4. Read amplifier
5. Index/Sector pulses
DIRECTION OF DISK MOTION
)IIIr
--l---BBDJ~~~~ifi~
0.0104
INCHES CORE CORE DATA
NOMINAL : I
--r--- GAP DJ--!~;;~-
120~INCH BAND
ERASE - - f-----
GAPS .0052
Figure 1-7. Magnetic Head Layout
Figure
1-9. Track Format (Upper Side)
OPERATION
. FLEXIBLE DISK (MINI-DISK)
Data
is recorded on the flexible disk on 88 concentric
tracks. The lower magnetic head
is offset relative to the
upper magnetic head in order
to make space for the press-
ure pads and the distance
of the tracks from the center of
the disk is different on the upper and lower surface. (refer
to figures 1-9 and 1-10).
The two tracks in line with the heads at anyone
time (one on the upper surface and one on the lower) is
known as a CYLINDER.
Sector Configuration
Each track contains 32 sectors with 180 bytes
of
data per sector. The sectors are marked by holes on the
disk (refer
to figure 1-9)". A transducer detects these
holes as the disk rotates and applies pulses
to the con-
troller. The sectors are numbered 0 to 31 and sector 0 is
marked by an index hole immediately preceding the sector
mark. The index hole
is located midway between the sector
31 and sector 0 holes.
READ/WRITE -..-,-.....,....-.,--
WINDING
CENTER
TAP
Figure 1-8. Head Schematic
ERASE
WINDING
Figure 1-10. Track Format (Lower Side)
For Form 2102141

Page 6 Burroughs -B9489 flexible Disk Drive
technical Manual
Introduction and Operation
Data configuration
The data within one sector consists
of the following:
(refer to figure 1-11).
1. Preamble (32 bytes of zeros)
2. Sync byte (2 bytes)
3. Address (2 bytes)
4. Data
(180 bytes)
5. Parity byte
(1 byte)
6. Postamble (remainder
of sector, bytes of zeros)
Recording Mode
The recording mode used
is Miller Frequency Mode
(M.F.M.) A comparison of the various recording medes i~
illustrated in figure 1-12. M.F .M. is a self clocking mode
(that is, it does not require a separate clock track) and it
enables approximately twice as much data
to be stored for
the same flux-change density.
M.F
.M. consists of a flux-change at the edge of a
data cell for a zero and a flux change
in the centre of a
cell for a one.
If a zero follows a one, a fluxchange is not
recorded. This
is recognised and corrected during read and.
the fluxchange density
is minimised.
180 DATA BYTES POST AMBLE
T:r l' ! BIT~ SECTOR ADDRESS
3 BITS ZERO ONE BIT HEAD ADDRESS
7 BIT CYLINDER ADDRESS
Figure 1-11. Sector Configuration
o 0
RZ
NRZ I
I
I
I
1 10 0
NRZl ~~~~
__ ":"---L._"':'-~ I I I
I I I
I I I
PE
DFM
MFM
Figure 1-12. Encocling Comparison
PARITY BYTE
MOD 2 SUM OF
CORRESPONDING BITS
OFALL DATA BYTES
o 0.0.0
I I
t t

Burroughs -B9489 Flexible Disk Drive Technical Manual Sec. 1 Page 7
Introduction
and Operation
FUNCTIONS
The Seek function is the command from the con-
troller
to the unit to move the heads to a new track. The
seek function sequence
is as follows:
1. A new track address
is applied to units.
2. A seek pulse
is applied from the controller to
the master or slave.
3. The carriage moves to a new track and settles.
4. The POSITION SETTLE signal
is applied to
the controller.
POSITION SETTLE is the signal that a write or read
operation may begin. Overlapping seek
is permitted and
consists
of performing a seek on one unit while a seek is in
progress on the other unit.
Write
A write
is initiated from the controller by making
WRITE ENABLE true.
If the Write lockout hole on the
disk jacket
is covered, the WRITE ENABLE signal enables
the write and erase drivers on the selected drive.
NRZ data (WRITE OATA) is supplied to the drive
in synchronisation with the OATA CLOCK which
is
generated in the disk drive.
The NRZ data
is converted to M.F .M. in the common
electronics (see figure
1-16).
The MFM data is then transferred to the selected
unit where
it controls the direction of current flowing
through the head.
The erase coils are also energised
to provide a "guard
band" of erased disk on either side of the data written.
The formatting
of the data into preamble, address
data, parity bits etc.
is a function of the controller.
As the disk passes over the selected head, the flux
reversals induce an alternating current into the coil
of the
head. This
is amplified, filtered for noise and digitised.
The digitised read information from the selected unit
is applied to the common electronics portion of the PCB.
On receiving READ ENABLE from the controller an
oscillator locks
onto the data providing a data sampling
window
and a READ CLOCK. The purpose of this oscill-
ator (phase locked loop) is to enable translation from
MFM to NRZ.
The READ OATA is then applied to the host, syn-
chronised with READ CLOCK.
The read operation ends when READ ENABLE from
the controller goes false. READ ENABLE
is made true
shortlyafter a sector pulse so
that the Phase Locked Loop
can lock in on the preamble prior
to the address and data.
READ ENABLE
is made false at the end of the sector.
PHYSICAL AND ELECTRICAL CHARACTERISTICS
Physical
Length
Width
Height
Weight
Shipping weight
Electrical
AC Power
17.25 inch
10 inch
5.62 inch
201bs.
231bs.
120V + 6%
-10%
(43.8 cm)
(25.4 cm)
(14.3 cm)
(
9.07 kg)
(10.43 kg)
50-60Hz 0.3 A per unit
DC Power +
5V ± 10%
+12V ± 10%
-12V ±10%
+24V ± 10%
Heat dissipation 75W
RECORDING CHARACTERISTICS
Format
Number
of cylinders per disk.
Number
of sides per disk
Number
of tracks per disk
Sectors per track
Sectors per cylinder
Sectors per disk
Data bytes per Sector
Data bytes per Surface
Data bytes per disk.
Tracks per inch
Bit density (Bits per inch)
Recording mode
Data access
Disk rotation speed
Average latency
Track
to track
Maximum access time
Data transfer rate
2.0 A per master unit
1.8 A per slave unit
0.3 A per unit
0.3 A per unit
2.25A per unit
88
2
176
32
64
5,632
180
506,880
1,013,760
64
4,774 max.
M.F.M.
370 rpm
80ms
47 ms
516 ms
375 K bits/second
For Form 2102141

Page 8 Burroughs -B9489 Flexible Disk Drive Technical Manual
Introduction and Operation
FLEXIBLE DISK
The flexible disks are made from Mylar, or a similar
material, 0.003 inch thick. The disk
is coated with a 110
microinch thick layer of iron oxide/polymer. Figure 1-13
illustrates the dimensions of the disk.
Jacket
Figure
1-14 illustrates the dimensions of the disk
jacket. The inside
of the jacket is covered with cleaning
tissue
to keep the disk clean.
Disk Handling
The disk should be used under the following en-
vironmental conditions:
Temperature: 50°F
to 125°F (10°C to 51.6°C)
Humidity:
8% to 80%
The disk should be stored under the following con-
ditions:
Temperature:
Humidity:
30°F to 125°F (_1°C to 5 1. 6°C)
5% to 90% No moisture to be
present on the disk.
The following procedures and precautions should
always be observed in order to avoid damaging the disk.
if Always put the disk back in the envelope when
out of the drive.
INDEX HOLE HALFWAY
25
~bl~~EN TWO SECTOR
32 SECTOR HOLES
0.05 INCH DIAMETER
/ .
Figure 1-13. Disk
\-
2. Always keep the disk in the envelope in the
ten pack box.
3. Always return the empty envelope to the ten
pack box.
4. Treat the disk
as fragile and easily damaged.
5. Use a felt tip pen to write on the disk label (a
pencil or ball point pen will damage the disk).
6..
DO NOT touch the magnetically coated (brown)
surfaces.
7. DO NOT leave the disk lying around on work
surfaces.
8.
DO NOT put objects, including papers, on top
of the disk.
9. DO NOT expose .the disk
to temperatures
above 125°F (51.6°C).
10. DO NOT allow the disk to become contamin-
ated by tea, coffee, cigarette ash or similar
contamination.
11.
DO NOT put a contaminated disk into a drive.
12.
DO NOT attempt to load a disk into a drive
that is switched off. Damage to the center hole
may result.
13.
DO NOT expose a disk to magnetic fields in
excess
of 50 oersteds. Always remember that
tools can become magnetised.
14.
DO NOT fit labels other than those supplied
in the ten pack box.
15.
DO NOT handle the center hole of the disk.
8.00 INCHES
0.057 INCHES
Figure 1-14. Jacket
SECTOR/INDEX HOLE
WRITE LOCKOUT HOLE
0.30 INCHES DIAMETER

Burroughs -B9489 Flexible Disk Drive Technical Manual Sec. 1
Page 9
Introduction and Operation
OPERATING PROCEDURES
Indicators and Control (refer to figure 1-15)
Door Release Bar
Depressing the release bar unlatches the door and
receiver for disk insertion. Closing the door securely auto-
matically latches it shut.
Write Enable Indicator
When the Write Enable (red) indicator
is illuminated
it indicates
that the disk in the unit can be written on and
that old data will be destroyed. When the red indicator
is
out it indicates that the disk caEnot be written on and data
is protected.
File Operational Indicator (File Op.)
When the File Op (blue) indicator is illuminated it
indicates that a disk
is inserted, up to speed and is in an
operational state.
Disk Insertion
1. Ensure that the power is ON.
2. Press blue Door Release Bar to open the door.
3. Remove disk from envelope.
4. Insert the disk into the drive, head access slot
first, with the label away from the release bar
(see figure
1-14 and 1-15).
5. When the disk is correctly inserted close the
door. When the blue File Op indicator
is
illuminated the unit is ready.
NOTE:
If the disk is inserted the wrong way, the File
Op. indicator will
not illuminate.
Disk Extraction
1. Wait until the system has completed processing
with the disk.
2. Press Door Release Bar on the unit.
3. Extract the disk.
4. Immediately return the disk to its envelope.
5. Close the door
of unit.
ELECTRICAL INTERCONNECTIONS
HOST TO MASTER INTERFACE
Table 1-1 contains the logic interface signals between
the host system and the master drive. Each signal line
is
formed into a twisted pair with its ground return.
CABINET SELECT/ -
is used to select one of the two
drive cabinets. When CABINET SELECTI
is set to logic 1
cabinet 0
is selected. When CABINET SELECT/is set to
logic 0 cabinet 1
is selected.
Table
1-1. Logic Interface Between Host System And
Master Drive
SIGNAL GROUND
PIN PIN
-"--
42 32 Cabinet Select/
47 30 Unit Select/
'11 -12
Head Select/
15 31 Address-1/
17 16 Address-2/
50 33 Address-4/
49
48 Address-8/
From Host System
13 14
Address-16/
6 25 Address-32/
7 8
Address-64/
43" 26 Seek/
46
29 Write Enable/
44 27 Write Data/
45 28 Read Enable/
4 5 Read Data/
40
23 File Operational/
39 22 Positioner Settled/
34 18 Write Inhibit/
36 20 Index/ From
Disk Drive
35
19 Sector/
37
21
Illegal Address/
41 24 Seek Incomplete/
2 3 Data Clock/
DOOR
~"
III I IIIl
J
DOOR RELEASE BAR
WRITE ENABLE INDICATOR·
(RED)
FILE OPERATIONAL INDICATOR
(BLUE)
Figure 1-15. Operator Controls
For Form 2102141

Page 10
Burroughs -B9489 Flexible Disk Drive TeGhnical Manual
Introduction and Operation
UNIT SELECT/ - is used to select either the master drive
or the slave drive. When UNIT SELECT/
is set to logic 1
the master drive is selected. When UNIT SELECT/is set to
logic 0 the slave drive is selected.
HEAD SELECT/ -
is used to select one of the two heads.
When HEAD SELECT/is set
to logic 1 side 0 of the disk
is selected. When HEAD SELECT/ is set to logic 0 side 1
of the disk is selected.
ADDRESS-I/ through ADDRESS-64/ -select the
cylinder address. The cylinder address
is coded in binary.
When
ADDRESS-I/ is set to logic 0 and all the other
ADDRESS signals are set to logic 1cylinder 01 is address-
ed.
SEEK/ - is used to start a positioner movement to the
address selected by
ADDRESS-I/ through ADDRESS-64/.
This signal also causes selection and mechanical loading of
the head selected by HEAD SELECT/. The positioner move-
ment
and head selection are started by SEEK/ changing
from logic 0 to logic
1.
WRITE ENABLE/ - is used to enable writing data onto
the disk. When WRITE ENABLE/ is set to logic 0 data is
written onto the disk.
WRITE DATA/ -
is the data tobe written onto the disk.
When WRITE DATA/
is set to logic 1a data 0 is written
onto the disk. When WRITE DATA/ is set to logic 0 a data
1 is written onto the disk.
READ ENABLE/ -
is used to enable reading data from
the disk. When READ ENABLE/
is set to logic 0 data is
read from the disk.
READ DATA/ -
is the data being read from the disk. A
data 0 bit from the disk will set READ DATA/ to logic
1.
A data 1 bit from the disk will set READ DATA/ to logic O.
FILE OPERATIONAL/ - is set to logic 0 if a disk is in
the drive, the disk
is rotating within 10% of full speed and
the positioner has recalibrated to track 00.
If FILE OPER-
ATIONAL/
is set to logic 1 all signals from the drive are
invalid.
POSITIONER SETTLED/ - is set to logic 1 when:
1. FILE OPERATIONAL/ is set to logic 1,
2. The positioner is in motion after a SEEK/
signal, or,
3. A head solenoid is in motion after a SEEK/
signal.
WRITE INHIBIT/ -
is set to Logic 0 if the disk in the unit
selected
is write protected.
INDEX/ -signal pulses to logic 0 when the index hole
on
the disk is detected.
SECTOR/ -signal pulses to logic 0 when a sector hole on
the disk is detected.
ILLEGAL ADDRESS/ -
is set to logic 0 if the ADDRESS/
lines exceed decimal 87 when SEEK/ changes from logic 0
to logic 1.
SEEK INCOMPLETE/ -. is not used and is always set to
logic
1.
DATA·CLOCK/ - isused to strobe the data on the WRITE
DA TA/ and READ OATA/ signal lines.
MASTER DC SUPPLIES
Table 1-2 contains the DC supplies to the master
drive. Each supply line
is formed into a twisted pair with
its return.
All DC returns are connected together on the
master drive.
Table
1-2. DC Supplies To The Master Drive
PIN
LINE
1 +24V
2 +24V Return
3 ±12V Return
4
-12V
5 +12V
6 +24V
7 + 5V Return
8 +5V
9
-12V
MASTER DRIVE TO SLAVE DRIVE INTERFACE
All DC, ground and logic signals are transferred from
master drive to slave drive
on one 40-way cable.
Figure
1-16 shows the master drive to slave drive
interface. READ OATA and WRITE DATA are
both en-
coded in M.F.M.
LINE POWER AND GROUNDING
The host system must provide line power to both
the master drive and the slave drive.
Pin
1. Not Connected
2. Not Connected
3. Line
4. Neutral
A ground
stud is provided adjacent to the line
connector.
CAUTION
ON EACH DRIVE THIS GROUND STUD MUST
BE CONNECTED TO THE HOST SYSTEM.